Posted
by
CmdrTaco
on Thursday May 27, 2010 @08:41AM
from the stupid-newton dept.

astroengine writes "Life is good in the Solar System. We have Jupiter to thank for that. However, if the gas giant's orbit were a little more elliptical, there's every chance that Earth would become rather uncomfortable very quickly. Researchers looking at the zoo of exoplanets orbiting distant stars have simulated several scenarios of differing exoplanet orbits and find that many don't resemble our cozy Solar System. In fact, weird exoplanet orbits may be the deciding factor as to whether extraterrestrial life can form or not."

In fact, weird exoplanet orbits may be the deciding factor as to whether extraterrestrial life can form or not.

Not sure the word 'fact' belongs in that sentence with the rest of the wild speculation. I do however want to donate to your fund but only when facts become the endpoint of extra-terrestrial flavoured cosmology and not the spark for futurology [wikipedia.org]!

Sounds like another Gleisian subspace mail scam to me. Let me guess, your name is 'Reverend' Tsmünqtll e'Eiïgåk, and you represent the Space Pope and all the starving spawnlings left over from the Second Great Tri-Moon Conflict.

I guess one of the mods must have been unimpressed, despite the fact that the linked fiction discusses a whole lot of stuff that other commenters mentioned farther down. Not a bad mod; if he thought it was overrated, so be it. Still disappointing (the story is exactly one week old; I hacked it out in about half an hour).

Oh well. There'll be more where that came from. I don't need the karma but I thought some of you might be interested. At least it wasn't modded "offtopic."

Complex life is another thing, of course... (or - we're frakked, because the aliens will turn out to be total badasses; due to evolving in very harsh conditions;p )

I'm guessing where they evolved will make precious little difference, we've built tools to let us survive far more than our bodies could take. What's a little bone exoskeleton against a kevlar vest? I'm fairly sure it's only in Avatar you can fire a machine gun all over a beast's face and not have it become a bloody pulp.

However, don't forget that the tools are also influenced by different circumstances.

If they, by using your example, would be naturally more armored (plus what's stopping them from also adding artificial armor, even to the point of modifying bone exoskeleton into a kind of composite armor that our modern tanks use?) - there could be pressure present to develop more effective weapons. If they would evolve in a place with 2g, they would be able to effortlessly carry a cargo equal to their mass when on Earth (t

But perhaps a badass exoskeleton life form wouldn't be that smart. Think of the Alien movies... they were highly evolved, but not really intelligent. Probably because they became such efficient killers that they never had to outsmart other animals. Which, as a result, would mean that unless we had to conquer a planet, we would never encounter such beasts. And if we did, I would hope that science would have had made enough advances allow us to effectively kill them seeing that we were able to overcome intergalactic travel.

Point #1: there's no such thing as "highly evolved". You and I (or the xenomorph) is no more highly evolved than an mold spore. We've all evolved in parallel to best fit into our respective environments, if we weren't then we'd be extinct.

Point #2: the xenomorph didn't evolve. It was a genetically engineered weapon ready to be dropped out of the bomb bays of the derelict alien spaceship, but something went wrong.

Here's the situation as I understand it (someone correct me if I get some of this wrong):

The line of organisms that we're descended from has changed quite a bit over time. Other lines have not changed much because they were sufficiently well-suited to their environment already. The theory of common ancestry says that we're all descended originally from one, or a small handful of the earliest forms of life. As life became more distributed, evolutionary forces shaped the populations in each environment int

Well, yes and no. In a way everything is "evolved" but you can also put them to absolute tests of logic, memory, pattern recognition and so on not entirely unlike an IQ test for humans. In that sense some species will be smart and others less smart, depending on what evolutionary path they've taken. Whether that means they're less evolved or not really depends on the logic of the scale. The reason we see it as a goal is because to us it signifies a different stage of evolution where it's not about adapting

Of course if the environment changed drastically, such as through a worldwide nuclear exchange, cockroaches could easily be at the upper end of intelligence on the planet again. Intelligence may give us the ability to adapt nature to our needs, but it also gives us the ability to destroy ourselves. So, while I see your point about intelligence being seen as "more evolved", it's still just one direction and one outcome. It's not necessarily the best one for long-term survival of the species.

For complex life to develop, you need conditions that do regularly provide evolutionary pressure, without completely wiping out all life.

Asteroid impacts are fine and even very useful for wiping out stagnant populations (like the dinosaurs) and giving room for new species to develop into, but they shouldn't be so big that they demolish the entire planet, or occur so often that no life is possible on the surface of the planet. Jupiter plays a huge role in that.

But there are also other factors. I'm pretty sure that our big moon and the tides it generates are a big factor in creating ever changing environments that provide a lot of opportunities and evolutionary pressure for populations, and that's all caused by a devastating Mars-sized impact. But another one like that would easily wipe out all life here.

Weather, seismic activity, it all plays a role. I definitely think our planet has a good chance of being reasonably unique.

True, but highly elliptical orbits pose not only the problem of harsh conditions, but of rapidly changing, oscillating conditions. This becomes a problem for the evolution of a biochemistry because every complex chemical system is only stable in a rather narrow interval. If the oscillation is large enough, there might just be no stable biochemistry possible.

Given that you need a reasonable amount of complexity to implement the basic necessities of life, in particular information storage, as well as a metabolism, I don't see much of an alternative to a carbon-based biochemistry. Carbon-based chemistry is the most versatile system, able to build a near infinite variations of molecules - this is a singular property among all the elements.

However, organic molecules tend to be not overly stable outside of a rather small temperature range. On the one hand, this is good for life, because it provides the necessary chemical reactivity and flexibility to make a living system possible. On the other hand, this severely limits possible habitats for extraterrestrial life. On the gripping hand, the conditions on Earth are not just favourable for any random biochemistry, they are favourable for the most complex class of chemical compounds possible. This does not exclude the possibility of other biochemistries adapted to other conditions, it does, however limit the set of possible conditions for life.

True, but highly elliptical orbits pose not only the problem of harsh conditions, but of rapidly changing, oscillating conditions.

Yes, but there are many other factors to consider. For example, with a highly elliptical orbit, a planet would spend far more time in the outermost portion of its orbit than it would spend close to its sun. So while the orbital summer experienced might be severe, it would also be brief. Here on earth all sorts of lifeforms exhibit the ability to survive brief climatic extremes

I generally agree - but it hugely depends on the orbit in question. The range of difference in conditions can't really exceed the stable range of the chemistry making up a particular form of life by much. As I argued, this has most likely to be carbon based. Of course this still leaves the possibility of life on such planets, but the probability is in my opinion much lower than on planets with more stable orbits. Moons - now they are a completely different question. I completely agree with your points there

Certainly, I don't disagree that highly elliptical orbits which literally fry a given world for months at a time before plunging it into the freezing depths of a given solar system for years would represent a potentially insurmountable challenge, at least to complex surface life.

I do wonder though if we might end up finding bizarre worlds in what might be otherwise be considered inhospitably elliptical orbits, where the "fry" phase turns out to be just enough energy to, for example, keep a global ocean from

You need a working biochemistry before you can evolve anything. You are at best proposing a mechanism how life could move into a more extreme environment - and then there are still limitations. Thermodynamics is one unforgiving bitch.... There still has to be a somewhat stable environment to kickstart the process. And yes, you are of course right that this could be a local zone of beneficial conditions. That still lowers the probability of the process, though - and I have the suspicion that this probability

If it were not that I were residing on the very same planet, I would find it unthinkable that such a planet could exist. Things with low probabilities do happen, especially during billions of years and as yet uncountable floating rocks.

This is one of those cases where the Anthropic Principle is very relevant: had such a planet been impossible, there wouldn't be anyone around to consider such a planet would be unthinkable. The only universe that can be observed is one where such a planet is possible.

Of course they do. Obviously it happened at least once. The question I am trying to discuss is not whether such things can happen, but rather how often we would expect them to happen. That's all. My point still stands - planets with highly excentric/elliptical orbits are less likely to develop life than stable planets like earth. A lot of our physicochemical and biochemical knowledge speaks for that. Now, of course, we suffer under the bias of our exoplanet detection methods, so I would not draw conclusions

Life is based on chemistry and on thermodynamics. There are constraints that have to be universal. Life needs a certain complexity of the underlying chemistry that allows somewhat stable information storage and the possibility of teleonomic structures paired with enough reactivity to actually allow a metabolism. Life needs thermodynamic boundary conditions that allow for dynamic equilibria. We can compare different environments with regard to these boundary conditions and give very rough estimates of relati

We know that Venus and Mars, if they had life at one point, don't have much now,

I have to say that is an assertion rather than a fact. We have not discovered much life on Venus or Mars yet, but consider that we have only sent a small handful of probes and rovers to either. We may have mapped the surface of Mars from orbit, but that doesn't mean we would have discovered whatever potential life may be there. Consider the fact that many of the Earth imaging satellite systems have a very hard time resolving pictures of humans on the surface (really, even getting 30 meter resolution of vis

Question is - where is the "optimal" point for such evolutionary pressure? I don't think we can assume we have it (who even knows in which direction is our deviation), even if our limited data suggest we're quite close (and for exactly what kind of life? We can probably assume that for complex biological one, sure, even it exists for few hundred millions years only - the rest of the time being dominated by bacteria...which still rule this place; but is it for "intelligent" life? So far we seem to be quite s

Asteroid impacts are fine and even very useful for wiping out stagnant populations (like the dinosaurs) and giving room for new species to develop into

Um I'm not aware of any evidence that dinosaurs were "stagnant". They were continuously evolving to fill niches as environments changed, and exceptionally successful at doing so.

The K-T Event was obviously "useful" from the perspective of us mammals since it gave us a chance to shine and fill niches the dinosaurs previously had. It's conceivable mammals still would have out-competed dinosaurs eventually, but anything but guaranteed. So from our perspective it was a good thing.

But saying the mass extinctions of the past were "useful" from a neutral viewpoint because they got rid of "stagnant" groups like the dinosaurs sounds like an unjustified value judgment to me.

Weather, seismic activity, it all plays a role. I definitely think our planet has a good chance of being reasonably unique.

Unique, sure. Snowflakes are unique, but the differences rarely matter.

What I'm saying is, sure there will be plenty of planets with properties that make it difficult if not impossible for life to evolve. Sure our planet has a unique set of circumstances. In between, there's a wide variety of possible planets where life could hypothetically evolve, just with a different path than ours. And so far there's little evidence that this wide gray area is unpopulated (though sadly little evidence *for* these planets, but our ability to detect those planets if they exist is quite limited).

Or we've evolved in extraordinarily harsh conditions without realizing it and the aliens think they have it easy.
"You guys only live for *how* many centuries each? And you require two people to pass on DNA to encourage evolutionary mutations so your spawn can adapt to future changes in your enviornment?!"

Obviously "weird" and "extreme" are relative terms.BUT, it seems reasonable to presume that inconsistency may be detrimental to formation of life.

Its one thing to evolve to adapt to an extremely hot location.But its another thing to adapt to a location that fluctuates between extreme hot and extreme cold, etc. Not saying its impossible, but probably more difficult.

Not so much dead, as with all the life hidden and trying to survive ("the strongest..." and all that; which somehow the point;p )

Accidentaly, it seems one of the best adaptations to harsch condition turned out to be...high intelligence. And if our level of it is far from greatest even for organic or, more generally, biological systems...

Not really.On earth life that becomes a total bad ass to use your words tends to come from a moderate climate.If it is too harsh then nobody does anything but just survive.Too soft and well no effort is really needed.

But this article suggests the origins of life, that's the very first living creatures, not diversification as we find on our own planet. It may be that very stable and nutrient rich solutions with very few variations are necessary to coddle the first stages of life into existence, after which evolutionary processes can start the whole "survival of the fittest" diversification of life, that causes life to evolve into an ability to dwell in more extreme climates. This would also explain why seas were a cradle

If anything, all of this could be mean that our system is quite weird; at least on average.

Possibly, but not likely. Our current planet detection methods are skewed toward finding the oddballs with high mass and highly elliptical low orbital periods. They induce the most wobble and occlude the most light from their stars. As such, they are the easiest to find over short observation periods.

Absolutely true. When the Square Kilometer Array (eventually) comes online, it will be possible to directly observe any exoplanet Earth-size or larger at a distance of 1 AU or greater from its sun at a distance of 100 LY from Earth, provided it is not perfectly reflective or perfectly dark within the range of frequencies being looked at. (If there's even one absorption line, the planet will be visible.) With the current design, at the limits given above, the head of the SETI Institute has stated that such a planet would resolve to one pixel. (That particular talk was fascinating, BTW.)

However, consider that most radio telescope arrays have nothing like that collecting area, nor do they have anything like the effective dish radius. Most radio telescope arrays simply can't directly observe exoplanets at any significant distance. This is why indirect observation and indirect measurements remain the norm.

"or - we're frakked, because the aliens will turn out to be total badasses; due to evolving in very harsh conditions"

Hmmm...

Since anything other then *your* native environment will probly seem 'harsh', especially if you have the habit of visting all sorts of planets, visitors will probably show up here and either stay in their ships as they hose us with directed-energy weapons or spray us with whatever biological goo does us as they wish us to be done. Unlikely that they will land and walk out all crip and

in toronto and montreal, they started building malls underground, and linking them up, so now you can practically roam the entire downtowns of these cities, all underground

in the distant future, us heroic stoic freedom fighting american movie hero archetypes will have to face invasions of the evolutionary future: the fearsome greater northern Canadian Humanoid Underground Dwellers

Meh. I thought it was obvious. We are polar bears that have adapted to hunting Humans by mimicking their behavior. Over time we have come to look just like them, unfortunately many have also become jerks as a result.

The problem is expecting life to continue to adapt if it lives on a tropical shore for millions of years, then the next year the sea freezes. A lot of factors have contributed to the evolution of life on Earth. Jupiter is large enough that it captures most large chunks of rock that could cause mass extinctions. A few have it Earth, but not nearly as many as without a large gas giant. If these happen too frequently, it's hard for the ecosystem to recover. We needed one thought to split off the moon. Without the tidal forces, the surface radioactivity would be much lower and mutation rates would be very low, meaning that evolutionary changes would take longer. Intelligent life might still have evolved, but it would have taken a lot longer.

I guess the tide serves a dual purpose, rising and falling tides will expose sea-dwelling life forms to the air, eventually a variant life form will evolve that can survive in both states, and that leads eventually to land dwelling organisms. On a world with no tide there'd be little opportunity for life forms to be stranded out of water in sufficient quantities for that mutation to take hold, or at least not in anywhere near the same timeframe.

I don't know, I mean how many amphibious life forms are there around the sea shore now, crabs maybe? Compare this to the number of actual amphibians which are in or near lakes or rivers, without tidal influence but quite susceptible to drying up, and I think that the idea that plate tectonics play a much more important role than the tides becomes clear. When plates shifted around they changed the climate, causing hot and cold spells depending on how much of them was near the polar caps, pulling vast quantit

You know, in all of these life on other planet stories, I've seen Jupiter touted as this savior planet because it prevents so many asteroid impacts here on Earth. That's all well and good for us, but who is to say that frequent asteroid impacts couldn't be an evolutionary pressure in and of themselves? I mean, perhaps a system that got bombarded by asteroids constantly would breed a lifeform that could go into some kind os suspended animation/hibernation period during the resulting sun blackout/dust cloud.

The problem is that evolution happens slowly. Asteroid impacts are a very abrupt change in the environment. They kill off a lot of species. A very slightly larger impact last time, and even the plants would have died, causing the atmosphere to lose its oxygen content and everything else to die within a few years.

Regular small impacts would be fine. Killing off 90% of the population periodically can spur rapid adaptation, as we've seen in antibiotic-resistant bacteria, but you just need one impact tha

That and the reverence they all share towards Ensign Jimmy O'Toole the only red shirt to survive 5 away team trips. He would have a safety poster in the lounge with his face on it and a finger pointing with the text: WWJD?!

First, Although the smaller inner planets would be hard pressed for life the moons of the gas giants orbiting closer to the sun could harbor life. There are only 8 (Or 9) planets in our solar system but there are over 300 moons.

Add to this that scientists seem to expect that life will only evolve on rocky earth like planets so it seems like a small chance. I know that the earth is the only example of life bearing planet that we have but to expect all life in the universe to exist in the same way that we do is narrow sighted. It would not surprise me to find out that there are fish swimming in a methane ocean on a distant planet in temperatures that would kill us.

Some day I fully expect to hear "It's Life, but not as we know it" and it not be a star trek reference. Well, Ok, how about only 1/2 a star trek reference.;)

Of course, the fact that we are finding these weird systems may simply be because they are the easiest to detect and all the stars with planetary systems like ours are thought to not have planets because we can't detect the planets using current methods and data.

Remember, Jupiter orbits the sun once every 12 years. So, if we were trying to detect our own solar system at 10 light years, how long would it take to detect Jupiter's effect on Sol's position?

You've hit the nail on the head. We're seeing these systems because either the gas giant is so close to the star that it obviously occludes the light and affects the radial acceleration of the star, or because their orbit extends far enough out from the star that it intersects with and modifies the surrounding debris cloud (think Oort).

Kepler and COROT are starting to return results. They'll need a decade or two to identify Jupiters and Kepler will need 4 or 5 years to identify an Earth or Mars.

Kepler and COROT are starting to return results. They'll need a decade or two to identify Jupiters and Kepler will need 4 or 5 years to identify an Earth or Mars.

Wouldn't it take Kepler at least 24 years and at most 36 to detect an "exo-Jupiter"? It needs to see two occlusions to even suspect that there is a planet, and a third occlusion to verify that the occlusion is in fact periodic. So that's at least two full orbits, and nearly 3 if we turned Kepler on right after the exo-Jupiter passed over its star

No, it's not safe to assume that all stars have planets around them... Many stars are binaries and closely orbiting binary stars might tend to toss any planets out of the system. Having said that, our closest neighbor (a trinary system of Proxima, Alpha Centauri A and Alpha Centauri B) is calculated to have somewhat stable orbital zones.

The likelyhood is that there will be something orbiting every star, because, as you say, it's all formed out of condensed clouds of stuff. Knowing they're probably there.

Remember, Jupiter orbits the sun once every 12 years. So, if we were trying to detect our own solar system at 10 light years, how long would it take to detect Jupiter's effect on Sol's position?

Possibly never. One of the reason we can detect so-called "hot Jupiters" is not just that their orbital period is very short, but also because, being close to their parent stars, the gravitational attraction of the planet upon the star is very, very strong. Gravity falls off in proportion to the square of the distance, so a Jupiter-sized planet in a Jupiter-like orbit makes its star wobble a lot less than a Jupiter-sized planet in an extremely tight orbit.

Yes, who says life on other planets has to be similar to what we see on Earth?

Basic chemistry. You need to have chemical bonds which are stable, but not so strong that it takes vast quantities of energy to reform molecules. Carbon compounds and water soluble chemicals are where it's at, baby.

That's fine, as long as you inflict earth's environmental conditions on your exoplanet. What happens if liquid water isn't available? Say, for example, the temperature is lower, or the atmospheric pressure is low. Water and carbon may not be the sweet spot anymore. Are you willing to make an arrogant statement like "There is no liquid water, therefore life is impossible"? I certainly wouldn't say something like that.

Other solvents - yeah, possible. Other base compounds than carbon? Well, I won't say impossible, but at least extremely unlikely. Boron has a somewhat complex, but in fact rather boring chemistry (sorry for the pun). Life needs complexity, flexibility and adaptability in its underlying chemistry. Si *might* be a candidate, with a silane chemistry quite similar to that of carbon - might be stable enough at lower temperatures to form some kind of biochemistry. Apart from that, I don't see any likely candidate

OTOH, I don't see how a form of primitive life can adapt to so much drastic and regular changes that are over a timespan of 1000 years, while some not so drastic and truly exceptional changes here have almost caused a total extinction of most species over that same timeframe.

OTOH, I don't see how a form of primitive life can adapt to so much drastic and regular changes that are over a timespan of 1000 years, while some not so drastic and truly exceptional changes here have almost caused a total extinction of most species over that same timeframe.

When you consider that the overwhelmingly vast majority of species that have ever existed have gone extinct, it's not so surprising anymore. Only those that are adapted well enough to handle the environment get to continue on. Sudden environmental changes can wipe out species pretty easily.

Is it really any surprise that life on Earth has evolved to not bother considering whether its views are self-suited, or truely objective, and thus has trouble grasping that its way of life isn't the only one?

However, it is potentially surprising that the orbits of other planets within the solar system could impact the ecosystems of each other in a significantly appreciable fashion.

Ironically, there is a school of thought that says the orbits of the planets in our solar system has only recently stabilized - ie, within recorded human history. It's not well supported and I have no idea about the scientific backing, but there is argument that the legends of old - of the gods fighting in the skies - is ac

Sure, so now when the world ends, we'll just blame it on Jupiter!
"Hey, Jupiter, why'd you lose weight?"
"Hey, Jupiter, how come you eat so much?"
"Hey, Jupiter, what happened to that cute red spot? Did you get it removed? Because I really thought it was sexy."
Why don't we just leave Jupiter alone, and quit being so judgmental?

As i said, kept evolving. Now the evaluation on in how many planets could evolve life now must take in account to be in a solar system with a configuration similar to our one (with gas giants making less extreme the orbits of planets). Is not the equation by itself, but how should be calculated one of the input numbers.

And, btw, the equation [wikipedia.org] is giving around 2 as result by now, dont treat it as there must be plenty of intelligent life sarching for us in our local vincinity.

We see the Universe the way it is, because if it was different, we wouldn't be here to see it.

On the contrary, we would be perfectly suited to survive in any universe that spawned us.

A few years ago, it was reported [newscientist.com] that without a moon life on earth would be impossible.

Now we are told any little difference in Jupiter's orbit would also render life impossible.

There seems to be a great tendency to suggest we live in a giant "Just So" story and could not exist in any other scenario, while at the same time we are finding life in the most inhospitable places imaginable.